1α,25-Dihydroxyvitamin D3 inhibits the differentiation and bone resorption by osteoclasts generated from Wistar rat bone marrow-derived macrophages

The steroid hormone 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH) 2D3] plays an important role in maintaining a balance in calcium and bone metabolism. To study the effects of 1 alpha, 25-(OH)(2)D-3 on osteoclast (OC) formation and bone resorption, OC differentiation was induced in bone marrow-derived mononuclear cells from Wistar rats with the addition of macrophage colony stimulating factor and receptor activator for nuclear factor-.B ligand in vitro. Cells were then treated with 1 alpha, 25-(OH)(2)D-3 at 10-9, 10-8 or 10-7 mol/l. OCs were identified using tartrate-resistant acid phosphatase staining and activity was monitored in the absorption lacunae by scanning electron microscopy. Expression levels of functional proteins associated with bone absorption, namely carbonic anhydrase II, cathepsin K and matrix metalloproteinase-9 were evaluated by western blot analysis. The results showed that 1 alpha,25-(OH)(2)D-3 inhibited the formation and activation of OCs in a dose-dependent manner and downregulated the expression levels of bone absorption-associated proteins.